Upgrading A C3 Corvette Cooling System - Cool It To Use It

Dewitt's Cooling System Makes All the Difference

One of the most critical and yet overlooked systems to be found on a classic Corvette is the cooling system. Anyone who has clocked any serious seat time in one of these machines has inevitably experienced the anxiety of steadily climbing temperatures, and the worry and grief that goes along with it. Nothing ruins a summer outing like a vehicle that simply won't keep its cool. Add a modified engine, lower gears, or even normal stock equipment like air conditioning, and the potential for heating problems is only exasperated.

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If you want cooling, this system from DeWitts delivers. The aluminum radiator is the same size as the original and is a bolt-in direct-fit, but the cooling capacity is stellar. The wide aluminum tubes and high-efficiency fins provide heat dissipation a regular copper/brass radiator just can't compete with. The dual-fan kit is the icing on the cake, moving a massive amount of air, but only when needed.

With most new vehicles, we tend not to give it a second thought, flying down desert highways in the searing heat of summer, A/C blasting, with nary a worry in a world. Contrast that to sweating with the A/C long switched off to preserve cooling capacity, fretting and concerned as the temperature gauge continues to climb. Sometimes, evasive action is called for, slowing to a fraction of the flow of modern traffic, or even turning on the heater in a desperate bid to shed additional BTUs with the meager capacity of the heater core. Take the opposite scenario, you're trapped in the snarl of urban traffic with nowhere to go, idling and crawling with no possibility of escape; the temperature gauge begins to soar. You suffer the impending doom, again perhaps trying the heater trick, or continuously clutching, or going to neutral and holding some revs in a frantic effort to shave critical degrees. If enough heat reaches the carb, you'll experience the double indignity of an engine boiling the fuel and continually trying to stall. A nightmare scenario? Actually, it's all too common.

These kinds of problems are so prevalent, in fact, that in many cases the tendency to overheat is a primary reason many owners simply will not drive their classic Vette. A few bad experiences as those just described are more than enough for many owners to opt for permanent dry-dock in the confines of a garage. So, what makes a modern machine so capable of coping in situations which may push our older Vettes over the edge? There are a variety of factors, not the least of which include higher overdrive gearing to reduce the revs, and the seldom considered effects of built-up rust and corrosion in the water jackets. Be that as it may, almost all modern machines feature large aluminum radiators with high-efficiency electric fans.

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01 Removing the radiator on a mid-'70s C3 is a real chore if you are not aware of the process, but not really bad at all if you know how it's done. To gain working access, it is best to start by removing the hood.

For the ultimate cooling in a classic Vette, it pays to take a page from the advancements put forth by the modern OEMs. First, consider that at best, many older Vettes were marginally equipped in cooling capacity, even when new. Although there are many factors involved in cooling efficiency, such as airflow, the fan/fan clutch condition, thermostat, and water pump, the bottom line comes down to one major factor-the radiator's ability to shed heat. When it comes to real cooling ability, this is the big-daddy factor that really counts the most. If that capacity is not there, you can fool with thermostats, trick water pumps, fans, airflow shields, gaskets, or all manner of magic elixirs and potions added to the coolant, and still come away frustrated. By contrast, bolt-in a radiator with heroic capacity to dissipate BTUs and fans to really move the air, and success is virtually guaranteed every time.

A perfect example of all we've aforementioned is our '76 Stingray. With only a mildly modded 350, this machine has ample get-up and go, but the combination of relatively low gearing and a marginal factory cooling system made it undrivable from any practical standpoint. At normal freeway speed, the temperature would climb precipitously, punctuated with convulsions of boiling and frothing when parked at the end of a run. On the other hand, crawling through traffic was a certain death sentence, sure to end with coolant breaching its confines to spill gracelessly on the tarmac below. Basically, the car was useless, but we knew what to do. Here there was no room to compromise; the plan was simply to bolt-in the best system we could find-a modern high-capacity radiator, complete with precisely controlled electric fans.

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Upgrading A C3 Corvette Cooling System - Cool It To Use It

If you want cooling, this system from DeWitts delivers. The aluminum radiator is the same size as the original and is a bolt-in direct-fit, but the cooling capacity is stellar. The wide aluminum tubes and high-efficiency fins provide heat dissipation a regular copper/brass radiator just can't compete with. The dual-fan kit is the icing on the cake, moving a massive amount of air, but only when needed.

01 Removing the radiator on a mid-'70s C3 is a real chore if you are not aware of the process, but not really bad at all if you know how it's done. To gain working access, it is best to start by removing the hood.

02 This Stingray has fairly low original mileage, but the engine shows obvious signs of repeated overheating. The rust stains on the aftermarket aluminum intake manifold and the nonstock thermostat gasket provides a clue. Check the stretched and swollen condition of the hoses, more evidence of repeated overheating and the resultant excessive coolant pressure.

03 The air-conditioning condenser, if so equipped, should come out first. Once the lines are disconnected, it unbolts at the core support, and then pulls straight up and out. Use extreme care when disconnecting the condenser lines since the fittings are fragile. Support the condenser side of the connection when wrenching the line fitting, and, of course, be certain that the system is properly evacuated of refrigerant.

04 Our radiator support was seriously rusted at the lower areas, a common malady with older C3s. We knew DeWitts would be able to cover this since they stock a range of new replacement radiator supports for most models.

05 To gain working clearance, the fan, belts, and radiator hoses were removed next. Don't attempt to remove the bulky fan shroud at this stage, no matter how much you wrestle, it won't come out yet without breaking it.

06 To continue with disassembly, the radiator core support needs to be unbolted. There are three bolts grabbing the sides of the support from the inner fender at each side, and two more at the bottom of the support.

07 Once unbolted, tilt the radiator support forward to gain the clearance needed to remove the shroud and then the radiator.

08 Something didn't look right behind the crankshaft pulley, and there we found an unexpected, nasty surprise. The rubber on the factory damper had given up, and the inertia ring separated from the hub, riding all the way back to the timing cover. Anytime you are working on an older Vette, keep a vigilant eye open for trouble. This will be easy to fix now, but could have caused quite a bit of damage had we not caught it.

09 Rather than just going back with another OEM damper, we went to a high-quality, SFI-rated, fail-safe No. 90000 damper from Professional Products. This 6.75-inch damper is a bolt-on replacement for our 350, and is fully degreed for accurate timing settings.

10 Our Vette had been run with plain water in the cooling system, and we were worried about rust and gunk from the water jacket fouling the new radiator. While it was apart, the thermostat and water pump were removed, and the water jackets were thoroughly flushed until all the loose rust and scale were cleaned. We also flushed the heater core circuit and then installed a new thermostat-cheap insurance.

11 Now was also the right time to replace the waterpump. We just used a rebuilt stocker. With the electric fans replacing the original mechanical unit, the pulley is simply bolted directly to the water pump's drive flange.

12 We really like the Spal electronic fan control that came with our DeWitts system. Rather than a simple thermostat/on-off, this system varies the fan capacity based on temperature. The wiring kit is complete and comes with most of the terminal connections already made.

13 Getting the radiator support in position started the DeWitts' install. Rather than trying to wrangle the bulky assembly with the radiator at once, this is the easier way to go, especially for a one-man installation. The lower two bolts were started a few threads for now, and then the support was tilted forward, as when the old radiator was removed.

14 With the core support tilted and tied forward, the radiator is more upright, making it much easier to slip the radiator down on its saddle mounts when working solo. The original saddles and top clamps fit the DeWitts radiator perfectly. It's a good idea to replace the rubber at these mounts when installing the new radiator.

15 Once the radiator was secured, the core support was tilted into proper alignment, and the bolts along the fender apron were installed. To ensure the fasteners line up, get all the bolts just started before cinching any of them down. Once they are all in place, they can be tightened.

16 We took the time to clean, detail, and paint the A/C condenser. It slips down over grommets at the bottom, and bolts up top with the outer fasteners from the radiator's upper mounting brackets.

17 The flat on the firewall just adjacent to the wiper motor seemed to be the perfect mounting point for the Spal control box. This position allows easy access to the programming buttons, and provides full view of the monitoring LEDs. The relay for the secondary fan fit right below. You can also mount the controller in a hidden position to retain an OEM appearance.

18 DeWitts' Direct-Fit radiator and dual-fan setup looks like it was born in our Corvette's engine bay. The system toys with anything our small-block can throw at it and has the reserve heat-rejection capacity to handle future engine mods with ease.